Switching device

ABSTRACT

A switching device is provided which comprises a pair of electrodes, and a insulating zone and a conductive or semiconductive zone that are provided between said electrodes. Another switching device is also provided which comprises a pair of electrodes, and a laminated structural body in which an insulating thin film and a conductive or semiconductive thin film are alternately laminated between said electrodes in the direction vertical to the surfaces of said electrodes. This device may be used for a switching process in which an electric circuit is switched from the switched off state to the switched-on state by irradiation of electromagnetic radiation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical switching device capable ofswitching an electrical circuit from the switched-off state to theswitched-on state by the irradiation of electromagnetic radiations (suchas visible light, ultraviolet rays, infrared rays, X-rays andgamma-rays.

2. Description of the Prior Art

Photoelectric conversion devices having been hitherto widely used,capable of switching electric circuits from a switched-off state to aswitched-on state by the irradiation of light or pulses of light includea photoconductive cell comprising a photoconductive material such as CdSand ZnO provided with ohmic contact electrodes, a p-n-p-n junctionoptical switch diode, etc. However, the former is disadvantageous inthat the switching speed is as low as about 100 msec. On the other hand,it is the p-n-p-n optical switch diode that can bring about on-offaction by utilizing photoelectromotive force caused by irradiating lighton p-n junctions of a semiconductor device, and this can have aswitching speed of from 0.05 to 0.10 μsec.

However, once it is placed in the on state, the current continues toflow by the action of self-retension even when the irradiation of lightis stopped. For returning it to the off state, it is necessary todecrease the circuit current by changing external conditions.

In addition to the above, there is recently produced on an experimentalbasis an optical switching device having the semiconductorhetero-structure super lattice structure provided with the long-periodstructure, comprising different kinds of semiconductors alternatelylaminated in layers (D.A.B. Millers, IEEE Journal of QuantumElectronics, 1985, Vol. QE-21, page 1462). It is impossible in such anoptical switching device to switch an electric circuit in a high speedaccording to the irradiation/non-irradiation of light. However, thematerials used for forming the above semiconductor hetero-structuresupper lattice are limited to inorganic materials such a GaAs and Si,and also a complicated process is required for producing it. There hasbeen no report on examples of optical-switching devices in which organicmaterials are used.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide an opticalswitching device formed with an organic material. Particularly, theobject of the present invention is to provide an optical switchingdevice employing an alternately laminated structural body comprising anultra-thin film structural body made of an organic material.

More specifically, the present invention is characterized by comprisinga device having alternately laminated structure formed by a pair ofelectrodes and an insulating zone and a conductive or semiconductivezone provided between said electrodes, particularly an organic devicehaving a laminated structural body formed by alternately laminating aninsulating thin film and a conductive or semiconductive thin film; andexhibiting non-linear current/voltage characteristics quite differentfrom that of conventional optoelectric conversion devices (ortransducers), when the irradiation/non-irradiation of light is repeatedon such a device while applying an electric field thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section illustrating a switching device of the presentinvention;

FIG. 2 is a diagram illustrating a measuring circuit used in Examples ofthe present invention;

FIG. 3A and FIG. 3B are graphs showing the optoelectric characteristicsof a switching device of the present invention;

FIG. 4 is an explanatory view diagramatically showing a method offorming the insulating layer comprising an organic coloring matter, ofthe present invention according to an LB process;

FIG. 5A and FIG. 5B are schematic views illustrating monomolecularfilms; and

FIGS. 6A, 6B and 6C are schematic views illustrating built-up films.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electrodes used in the present invention may include a great numberof materials including metals such as Au, Ag, Al, Pt, Ni, Pb, Zn and Sn,alloys of these, or laminated structure of these, and alsosemiconductors such as Si (single crystal silicon, polysilicon oramorphous silicon), graphite or silicide (nickel silicide or palladiumsilicide), GaAs, GaP, ITO and NESA or laminated structures of these, aswell as any other many materials. The pair of these electrodes may beeither the same with or different from each other. Such electrodes canbe formed according to conventionally known techniques for the formationof thin films, whereby the object of the present invention can besufficiently achieved. Here, in instances in which the insulating zonein the present device is constructed of an organic material, theelectrodes to be formed after the preparation of such an organicinsulating layer may preferably be formed according to the procedurescapable of forming a film under the condition of 300° C. or less, and,for example, there can be used electrodes formed in films according tovacuum vapor deposition or sputtering.

In utilizing the device of the present invention, the irradiation ofelectromagnetic radiations is always entailed, but the electrodes maynot be necessarily be those perfectly transparent to the radiations, asfor example visible light, metallic electrodes made of Au, Al, etc., canbe used if the film thickness is to be controlled sufficiently small.Such film thickness may preferably be 2,000 Å or less, more preferably1,000 Å or less.

Between the above electrodes, the alternately laminated structure isformed, comprising a conductive or semiconductive thin film and aninsulating film. In respect of the formation of the insulating thinfilm, there can be utilized the vapor deposition or molecular-beamepitaxy, and besides, there can be also utilized oxide films of SiO₂,Al₂ O₃, etc., as well as nitride films of Si₃ N₄, etc., depending on theconstitution of the device. In any cases, the film is required to beultra-thin, more specifically, the film may preferably have a thicknessof 500 Å or less, more preferably 200 Å or less, and still morepreferably 100 Å or less and 5 Å or more. Attention should be also paidto the presence or absence of the homogeniety in the in-plane directionand thickness direction of such an insulating thin film, as it maygreatly affect the device performances and the stability thereof.

A most desirable process for the formation of the insulating thin filmin preferred examples of the present invention may include an LB(Langmuir Blodgett) process.

According to the LB process, it is possible to readily form amonomolecular film, or a built-up film thereof, comprising an organiccompound having a hydrophobic part and a hydrophilic part in a molecule,on any of the electrodes or any substrate containing any of theelectrodes, and also possible to stably provide an organic ultra-thinfilm having a film thickness of a molecular length order and beinguniform and homogeneous over a large area.

The LB process is a process in which a monomolecular film or a built-upfilm thereof is prepared by utilizing the property that molecules mayform on a water surface a monomolecular film with hydrophilic groupsdownward directed, when the balance of both is appropriately kept in thestructure having the hydrophilic part and the hydrophobic part in amolecule (i.e., when the amphiphilic balance is kept).

The groups constituting the hydrophobic part may include all sorts ofhydrophobic groups such as saturated or unsaturated hydrocarbon groups,condensed polycyclic aromatic groups and linear polycyclic phenyl groupswhich are widely generally known. These may constitute the hydrophobicpart respectively alone or in combination of a plurality thereof. On theother hand, the groups most typical as the constituent factor of thehydrophilic part may include, for example, hydrophilic groups such as acarboxyl group, an ester group, an acid amide group, an imide group, ahydroxyl group, a sulfonyl group, a phosphoric acid group and an aminogroup (primary, secondary, tertiary or quaternary one).

It is possible to form the monomolecular film on the water surface solong as the molecules have the hydrophobic groups and the hydrophilicgroups in well-balanced combination. In general, these molecules forms amonomolecular film having insulating properties, so that themonomolecular built-up film can also show the insulating properties.Thus, they can be said to be very suitable materials for the presentinvention. By way of an example, there can be included the molecules asshown below.

(1) Molecules Having The π-Electron Level

Coloring matters having a porphyrin skeleton, such as phthalocyanine,tetraphenyl porphyrin, etc., azulene type coloring matters having asquarilium group and a croconic methine group as bonding chains, andcyanine type similar coloring matters bonded with twonitrogen-containing heterocyclic rings such as quinoline, benzothiazoleand benzoxazole, a squarilium group and a croconic methine group; orcondensed polycyclic aromatic compounds such as cyanine dye, anthraceneand pyrene, and linear compounds condensed with aromatic or heterocycliccompounds; etc.

(2) Polymeric Compounds

Polyimide derivatives, polyamic acid derivatives, polyamide derivatives,all sorts of fumaric acid copolymers, all sorts of maleic acidcopolymers, polyacrylic acid derivatives, all sorts of acrylic acidcopolymers, polydiacetylene derivatives, all sorts of vinyl compounds,synthetic polypeptides, biopolymers such as bacteriorhodopsin andcytochrome, etc.

(3) Fatty Acids

Carboxylic acids and carboxylates having a long-chain alkyl group, orfluorine-substituted compounds of these, esters having at least onelong-chain alkyl group, sulfonic acid and salts thereof, phosphoric acidand salts thereof or fluorine-substituted compounds of these, etc.

Of these compounds, it is desirable particularly from the viewpoint ofthermal resistance to utilize the high molecular compounds or to use themacrocyclic compound such as phthalocyanine. Especially, not only suchthermal resistance can be made excellent but also the film thickness perone layer can be controlled to about 5 Å by using the polymericmaterials such as polyimides, polyacrylic acids, all kinds of fumaricacid copolymers and all kinds of maleic acid copolymers.

Needless to say, in the present invention, the materials other than theabove can be also desirable for the present invention so long as theyare suited to the LB process.

The above amphiphilic molecules may form on the water surface amonomolecular film with the hydrophilic groups downward directed. Here,the monomolecular film on the water surface has a feature of atwo-dimensional system, wherein the formula of ideal gas:

    πA=kT

can be established between the area A per molecule and the surfacepressure π, when the molecules are scatteredly spread out, to form a"gaseous film". Herein, k represents the Boltsmann's constant, and Trepresents the absolute temperature. If A is made sufficiently small,the intermolecular mutual action can be strengthened to give a"condensed film (or solid film)" of a two-dimensional solid. Thecondensed film can be moved layer by layer to the surface of any objectsuch as resins or metals of various materials or shapes. Themonomolecular film or built-up film thereof can be formed by use of thisprocess, and the resulting film can be used as the insulating zone,namely, a potential barrier layer, for the optical switching device thepresent invention demonstrates.

Specific preparation process may include, for example, the processesdescribed below.

A desired organic compound is dissolved in a solvent such as chloroform,benzene and acetonitrile. Next, using an appropriate apparatus as shownin FIG. 4 of the accompanying drawings, the resulting solution is spreadover an aqueous phase 41 to form the organic compound into a film.

Next, a partition plate (or a float) 43 is provided so that the thusspread layer 42 may not be freely scattered to overspread, whereby thespreading area of the spread layer 42 can be limited to control thegathering of the film substance to obtain the surface pressure πproportional to the gathering. This partition plate 43 is moved tominimize the spreading area to control the gathering of the filmsubstance, and then the surface pressure is gradually increased, andthere can be set the surface pressure π suited for the preparation ofthe film. While maintaining this surface pressure, a substrate 44 ismoved vertically upward or downward, so that a monomolecular filmcomprising the organic compound can be transferred onto the substrate44. Such a monomolecular film 51 comprises a film in which the moleculesare arranged in regular order as schematically shown in FIG. 5A or FIG.5B.

The monomolecular film can be prepared as above, and the above operationmay be repeated to form the built-up film with a desired built-upnumber. The monomolecular film 51 can be transferred onto the substrate44 by not only the above-described vertical dipping process but also ahorizontal lifting process and a rotating cylinder process.

The horizontal lifting process is a process in which a substrate is madein horizontal contact with the water surface to transfer themonomolecular film, and the rotating cylinder process is a process inwhich a cylindrical substrate is rotated on the water surface totransfer the monomolecular film 51 onto the surface of the substrate 44.

According to the above vertical dipping process, the substrate 44 whosesurface is hydrophilic is drawn up from the water in the directioncrossing the water surface, thus forming on the substrate 44 themonomolecular film 51 comprising the organic compound, whose hydrophilicpart 52 comprising the organic compound faces to the substrate 44 (FIG.5B). If the substrate is moved upward and downward as mentioned above,the monomolecular film 51 is laminated layer by layer every step to forma built-up film 61. Since the direction of the film-forming molecules isreversed in the drawing-up step and the dipping step, this method canform a Y-type film in which the hydrophilic group parts 53a and 53bcomprising the organic compound face each other between the respectivelayers of the monomolecular film 51 (FIG. 6A).

In contrast thereto, according to the horizontal lifting process, themonomolecular film 51 whose hydrophobic part 53 comprising the organiccompound faces to the substrate 44 (FIG. 5A) is formed on the substrate44. According to this method, the direction of the film-formingmolecules does not alternate if the monomolecular films 51 are built-up,and there can be formed an X-type film in which the hydrophobic parts53b face to the substrate 44 in all the layers (FIG. 6B). To thecontrary, the built-up film 61 whose hydrophilic parts 52b face towardsthe substrated 44 in all the layers is called a Z-type film (FIG. 6C).

The methods of transfer of the monomolecular film onto the substrate arenot limited to the above processes, and there can be also employed amethod in which the substrate is pulled out from a roll into the aqueousphase, when a substrate with a large area is used. The direction towardthe substrate, of the above-mentioned hydrophilic part and hydrophobicpart is defined as a principle, and can also be changed by a surfacetreatment or the like of the substrate.

FIG. 1 is a cross-section of a switching device of the presentinvention. The switching device illustrated in FIG. 1 comprises asubstrate 44, provided thereon with a pair of electrodes (an upperelectrode 15 and a lower electrode 11) and an alternately laminatedstructural body comprised of an insulating thin film 12, a conductive(or semiconductive) thin film 13 and an insulating thin film 14 that aredisposed between said electrodes 15 and 11.

The insulating thin films 12 and 14 may preferably be formed in filmsaccording to the LB process described above.

In the present invention, metal films made of Al, Ag, Zn, Sn, Pb, etc.or alloy films of these and semiconductive thin films made of As₂ Se₃,CdS, ZnO, GaAs, Si (single crystal silicon, polysilicon or amorphoussilicon), etc. can be used as the conductive or semiconductive thin film13. In the present invention, such conductive or semiconductive thinfilm 13 is required to have a film thickness of 500 Å or less,preferably 100 Å or less, and more preferably 50 Å or less. Especiallywhen metals or alloys thereof are used, it may preferably have a filmthickness of 50 Å or less.

The conductive or semiconductive thin film 13 can be formed by usingconventionally known thin-film formation techniques, but, in particular,may preferably be formed according to a vacuum vapor deposition process,a cluster ion beam process, a CVD process, a plasma polymerizationprocess, an MBE process, or a sputtering process.

In the present invention, the insulating thin film can be formed with aporous polymer. In the present optical switching device, a conductive orsemiconductive zone in the form of micro-zones may be formed in adispersedly mixed state in the porous polymer. In the present invention,an insulating zone and conductive or semiconductive zone in the form ofmicro-zones may also be formed in the dispersedly mixed state by makingthe porosity highly dense.

In the optical switching device of the present invention, the interfaceat which the insulating thin film and the conductive or semiconductivethin film are joined may be in a discontinuous form.

The conductive or semiconductive zone used in the switching device ofthe present invention, particularly when formed at an outer mostsurface, may preferably be covered with an insulating zone. Such aninsulating zone may be constituted of the material of the kind same withor different from the insulating material provided on another electrode(lower electrode), and is formed according to the method as alreadydescribed. Then, the electrode (upper electrode) can be formed accordingto the method as described above.

In the present invention, the substrate 44 for supporting the thin filmslaminated with inorganic or organic materials as described above may bemade of any materials including metals, glass, ceramics, plastics, etc.,or there can be also used biomaterials having a very low thermalresistance.

The substrate 44 as described above may have any shape, but maypreferably be in the shape of a flat sheet, without being limited to theflat sheet at all. This is because the above film formation processeshave an advantage that whatever shape the surface of the substrate mayhave, the film can be formed following its shape.

The LB process is used in Examples of the present invention for theformation of the insulating thin film, but there can be used otherprocesses without limitation to the LB process, so long as they canproduce a very thin and uniform insulating thin film. Specifically,there may be included vacuum vapor deposition, electrolyticpolymerization, CVD, etc., thus broadening the scope of the materialsthat can be used.

As having been described also with regard to the formation of theelectrodes, any film formation processes may be used so long as they canproduce a uniform thin film on the insulating thin film, without beinglimited to the vacuum vapor deposition or the sputtering.

In the present invention, there is also no limitation in the materialsfor the substrate or the shape thereof.

The effect of the present invention will be summarized below.

(1) It is shown that the optical switching performances showing theresponse that can not be seen in the conventional optoelectricconversion devices (or transducers) can be attained by alternatelylaminating the thin film insulating layer and the thin film conductivelayer or thin layer semiconductive layer.

(2) By forming such a thin film insulating layer by an LB process, therecan be formed a device that can achieve with ease the film thicknesscontrol in the molecular order, and can have a high reproducibilitybecause of the excellent controllability, resulting in richproductivity.

Examples of the present invention will be described below.

EXAMPLE 1

Following the procedures shown below, produced was a sample having thestructure comprising a lower electrode 11, an insulating thin film 12, aconductive thin film 13, an insulating thin film 14 and an upperelectrode 15 (FIG. 1). On a glass substrate 44 treated forhydrophobicity by leaving it a whole day and night in saturated vapor ofhexamethyl disilazane (HMDS), Cr was deposited as a subbing layeraccording to vacuum vapor deposition to have a thickness of 300 Å,followed by further deposition of Au according to the same method (filmthickness: 600 Å) to form the lower electrode 11 in the form of a stripeof 1 mm wide. On this substrate, a 10-layer built-up film (filmthickness: about 40 Å) comprising polyimide monomolecular films wasformed by using an LB process, to provide the insulating thin film 12.

The process for preparing the polyimide monomolecular built-up film isdescribed below in detail.

Polyamide acid represented by Formula (1) was dissolved in a mixedsolvent of N,N-dimethylacetamide and benzene (1:1 V/V) (concentrationcalculated as a monomer: 1×10⁻³ M), and thereafter mixed with aseparately prepared 1×10⁻³ M solution of N,N-dimethyloctadecylamineusing the same solvent in the proportion of 1:2 (V/V) to prepare asolution of the polyamide acid octadecylamine salt represented byFormula (2). ##STR1##

The resulting solution was spread over an aqueous phase 41 (FIG. 4)comprising pure water of a water temperature of 20° C. to form amonomolecular film on the water surface. After the solvent was removedby evaporation, a float as a partition plate 43 was moved to make smallthe spread area to increase the surface pressure to 25 mN/m. Whilekeeping the surface pressure constant, the substrate fitted with theabove lower electrode was gently dipped at a speed of 5 mm/min in thedirection crossing the water surface, and thereafter gently drawn up ata speed of 3 mm/min to form a Y-type two layer monomolecular built-upfilm. By repeating such operation, a 10 layer monomolecular built-upfilm was formed comprising the polyamide acid octadecylamine salt. Next,the resulting substrate was dipped in a mixed solvent of aceticanhydride, pyridine and benzene (1:1:3) for 12 hours to form thepolyamide acid octadecylamine salt into an imide (Formula 3) as shownbelow, to obtain a 10 layer polyimide monomolecular built-up film.##STR2##

Next, on the surface of this polyamide monomolecular built-up film, Alwas deposited by vacuum deposition in the form of a stripe of 1 mm wide(film thickness: 20 Å), crossing in right angle to the lower electrode,to form the conductive thin film 13. In this step, the temperature ofthe substrate surface was kept to room temperature, and here the filmformation rate was controlled to 3 Å/sec. Thereafter, the inside of thechamber was returned to normal pressure, and the surface of theresulting Al conductive thin film was oxidized to form the insulatingthin film 14 comprising Al₂ O₃. After this step, the inside of thechamber was again evacuated, and Al (film thickness: 300 Å) and Au (filmthickness: 600 Å) were deposited in succession by vapor deposition toprovide the upper electrode 15.

The curent characteristics (V-I characteristics) obtained when a voltagewas applied between the upper electrode and lower electrode of thesample prepared in the above manner were measured. An electric circuitdiagram for that purpose, using an ammeter 21 and an input electricsource 22, is shown in FIG. 2.

As a result, the off state (resistance value: ca.10⁸ Ω) was shown underthe dark at an applied voltage of 1.2 V (FIG. 3A). On the other hand,under the irradiation of light (white light: 70 μW/0.55 cm²), the offstate was kept up to the threshold limit value voltage (Vth=0.8 V), butthe on state (resistance value: 10 Ω) was shown at the applied voltageexceeding this threshold limit value. The switching speed to this onstate was less than 1 μsec, and the interruption of the irradiaiton oflight immediately resulted in the switching to the off state. Theswitching speed in this instance was also less than 1 μsec.

EXAMPLE 2

On the glass substrate 44, Cr was deposited as a subbing layer by vacuumvapor deposition to have a thickness of 300 Å, followed by furtherdeposition of Au by the same method (film thickness: 600 Å) to form thelower electrode 11 in the form of a stripe of 1 mm wide. On thissubstrate 44, a 10 layer polyimide monomolecular built-up film wasformed according to the same procedures as in Example 1, to provide theinsulating thin film 12.

Next, on this polyimide monomolecular built-up film, an amorphoussilicon film was formed with a film thickness of 30 Å, to provide asemiconductive thin film 13. Here, the film formation was carried out bya glow discharge process [introduced gas: SiH₄, H₂ (volume ratio 1:9);rf power: 0.01 W/cm² ; pressure: 0.5 torr; substrate temperature: 250°C.; deposition rate: 40 Å/min]. Subsequently, a mixed gas comprisingsilane (SiH₄) and ammonia gas was introduced, and a silicon nitride (Si₃N₄) film was deposited with a film thickness of 15 Å (rf power: 0.02W/cm² ; pressure: 0.5 torr; substrate temperature: 250° C.; depositionrate: 50 Å/min), to form the insulating thin film 14.

Next, on the surface of this silicon nitride film Al (film thickness:300 Å) and Au (film thickness: 600 Å) were deposited in succession byvacuum vapor deposition in the form of a stripe of 1 mm wide, crossingin right angle to the lower electrode 11, to form the upper electrode15. On the sample thus obtained, the V-I characteristics were measuredin the same manner as in Example 1. As a result, there was shown thesimilar switching performance.

EXAMPLES 3 to 7

Samples were prepared in entirely the same manner as in Example 1 exceptthat the insulating materials shown in Table 1 were used to form theinsulating thin film 12, and the V-I characteristics were measured. As aresult, all the samples showed similar switching performance.

                                      TABLE 1                                     __________________________________________________________________________                                                Thickness of                           Materials for insulating thin                                                                    Layer               insulating thin                   Example                                                                            film 12            number                                                                             Conditions for film formation                                                                film (Å)                      __________________________________________________________________________    3    t-Butyl substituted lutetium                                                                     8    F = 25 mN/m    180                                    diphthalocyanine                                                         4    C.sub.10 H.sub.21 CCCC(CH.sub.2)COOH                                                             8    F = 20 mN/m; polymerized by                                                                  140                                                            irradiation of ultra violet                                                   light after film formation                       5    SOAZ (X)           8    F = 20 mN/m    120                               6    (Y)                10   After film formation by adding                                                                50                                    A methacrylic acid/styrene                                                                            N-hexadecyldimethylamine                              copolymer               (F = 25 mN/m), this was                                                       removed by dipping the film in                                                a n-hexane/acetic acid (50:1%)                                                solution                                         7    Bacteriorhodopsin  8    F = 20 mN/m    --                                __________________________________________________________________________     ##STR3##                                                                      ##STR4##                                                                 

EXAMPLE 8

On a glass substrate, Cr was deposited as a subbing layer according tovacuum vapor deposition to have a thickness of 300 Å, followed byfurther deposition of Au according to the same method (film thickness:600 Å) to form a lower electrode in the form of a stripe of 1 mm wide.On this substrate, a silicon nitride (Si₃ N₄) film was deposited with afilm thickness of 40 Å by a glow discharge process [introduced gas: aSiH₄ /NH₃ mixed gas (SiH₄ : H₂ : NH₃ =2:18:80 by volume); rf power: 0.02W/cm² ; pressure: 0.5 torr; substrate temperature: 300° C.; depositionrate: 60 Å/min], to form an insulating zone.

Next, on the surface of this silicon nitride film, Al was deposited byvacuum vapor deposition (film thickness: 20 Å) in the form of a stripeof 1 mm wide, crossing in right angle to the lower electrode, to form aconductive zone. Thereafter, the inside of the chamber was returned tonormal pressure, and the surface of the resulting Al conductive layerwas oxidized to form an insulating zone. Subsequently, the inside of thechamber was again evacuated, and Al (film thickness: 300 Å) and Au (filmthickness: 600 Å) were deposited in succession by vapor deposition toprovide the upper electrode.

The current characteristics (V-I characteristics) ovtained when avoltage was applied between the uper electrode and lower electrode ofthe sample prepared in the above manner were measured (The instance inwhich a positive charge was applied to the upper electrode was regardedas the direction of normal flow). As a result, similar to thecharacteristics shown in FIG. 3A, the off state (resistance value: ca.10⁸ Ω) was shown under the dark at an applied voltage of 1.2 V. On theother hand, under the irradiation of light (white light: 70 μW/0.55cm²), the off state was kept up to the threshold limit value voltage(Vth=0.8 V), but, similar to the characteristics shown in FIG. 3B, theon state (resistance value: ca. 10 Ω) was shown at the applied voltageexceedin this threshold limit value. The switching speed to this onstate was less than 1 μsec, and the interruption of the irradiation oflight immediately resulted in the switching to the off state. Theswitching speed in this instance was also less than 1 μsec.

EXAMPLE 9

A lower electrode and an insulating zone comprising Si₃ N₄ were formedin the same manner as in Example 8, followed by formation of anamorphous silicon film with a film thickness of 40 Å by a glow dischargeprocess to form a semiconductive zone (introduced gas: SiH₄, H₂ ; rfpower: 0.01 W/cm² ; pressure: 0.5 torr; substrate temperature: 300° C.;deposition rate: 40 Å/min). Thereafter, the surface layer part (about 10Å) of this amorphous silicon film was formed into silicon nitride (Si₃N₄) according to a thermal nitriding process. Next, Al (film thickness:300 Å) and Au (film thickness: 600 Å) were deposited in succession byvacuum vapor deposition in the form of a stripe of 1 mm wide, crossingin right angle to the lower electrode, to form an upper electrode. Onthe sample thus obtained, the V-I characteristics were measured in thesame manner as in Example 1. As a result, there was shown the similarswitching performance.

EXAMPLE 10

An Cr-Au lower electrode and a Si₃ N₄ insulating zone were formed in thesame manner as in Example 8, followed by vacuum vapor deposition of Ag(film thickness: 20 Å) to form a conductive zone. Subsequently, asilicon nitride (Si₃ N₄) film was deposited with a film thickness of 15Å by a glow discharge process. After this step, Al (film thickness: 300Å) and Au (film thickness: 600 Å) were deposited in succession by vacuumvapor deposition in the form of a stripe of 1 mm wide, crossing in rightangle to the lower electrode, to form an upper electrode. With thesample thus obtained, the V-I characteristics were measured in the samemanner as in Example 1. As a result, there was shown similar switchingperformance.

EXAMPLE 11

A sample was prepared in the same manner as in Example 10 except thatthe conductive zone comprised of Ag was replaced by a semiconductivezone comprised of ZnS (film thickness: 40 Å) (by an ion cluster beamprocess; accelerated voltage: 3 kV; substrate temperature: 150° C.;deposition rate: 40 nm/min). On the sample thus obtained, the V-Icharacteristics were measured in the same manner as in Example 1. As aresult, there was shown similar switching performance.

We claim:
 1. A switching device, comprising:a laminated structurecomprising a pair of electrodes, and at least two insulating zones and aconductive or semiconductive zone that are provided between said pair ofelectrodes, and a means for applying electromagnetic radiation to saidlaminated structure, wherein said conductive or semiconductive zone isprovided between said insulating zones and has a thickness of 5 Å to 100Å, and wherein said switching device is switched from an off-state to anon-state under application of a voltage exceeding a threshold voltagewhen said laminated structure is exposed to electromagnetic radiation.2. The switching device of claim 1, wherein said conductive orsemiconductive zone is disposed separate from said electrodes throughthe interposition of said insulating zone.
 3. The switching device ofclaim 1, wherein said insulating zones and conductive or semiconductivezones are respectively formed by alternately laminating insulating thinfilms and conductive or semiconductive thin films to form a laminatedstructural body.
 4. The switching device of claim 3, wherein saidinsulating thin films have a film thickness of 10 Å to 500 Å.
 5. Theswitching device of claim 3, wherein said conductive or semiconductivethin films have a film thickness of 5 Å to 100 Å.
 6. The switchingdevice of claim 1, wherein said insulating zones comprise monomolecularfilms or monomolecular built-up films consisting of an organic compound.7. The switching device of claim 6, wherein said monomolecular films ormonomolecular built-up films are insulating thin Langmuir-Blodgettfilms.
 8. The switching device of claim 7, wherein said insulating thinfilms comprise Langmuir-Blodgett films comprising a compound having a πelectron level, a polymeric compound or a fatty acid.
 9. The switchingdevice of claim 1, wherein said insulating thin films are oxide ornitride films.
 10. The switching device of claim 1, wherein saidinsulating zones comprise a conductive metal-oxide film.
 11. Theswitching device of claim 1, wherein said conductive or semiconductivezone comprises a conductive or semiconductive thin film, and whereinsaid conductive or semiconductive thin film comprises a film made of ametal selected from the group consisting of Al, Ag, Zn, Sn and Pb or analloy thereof, As₂ Se₃, CdS, ZnO, GaAs or Si including single crystalsilicon, polysilicon or amorphous silicon.
 12. The switching device ofclaim 1, wherein said conductive or semiconductive zone has a thicknessof 5 Å to 50 Å.
 13. The switching device of claim 3, wherein saidconductive or semiconductive zone has a thickness of 5 Å to 50 Å. 14.The switching device of claim 1, wherein one electrode islight-transmissive.
 15. The switching device of claim 1, wherein saidelectrodes have a thickness of 2000 Å or less.
 16. A switching device,comprising:a laminated structure comprising a pair of electrodes, and afirst insulating zone, a second insulating zone and a conductive orsemiconductive zone that are provided between said electrodes, and ameans for applying electromagnetic radiation to said laminatedstructure, wherein said conductive or semiconductive zone is providedbetween said first insulating zone and second insulating zone and has athickness of 5 Å to 100 Å, wherein one electrode is made of Au, and saidinsulating zone adjacent to said one electrode contains a monolayer ormultilayer film of an organic compound, and wherein said switchingdevice is switched from an off-state to an on-state under application ofa voltage exceeding a threshold voltage when said laminated structure isexposed to electromagnetic radiation.
 17. A switching device,comprising:a laminating structure comprising a pair of electrodes, andat least two insulating zones and a conductive or semiconductive zonethat are provided between said pair of electrodes, and a means forapplying electromagnetic radiation to said laminated structure, whereinsaid conductive or semiconductive zone is provided between saidinsulating zones and has a thickness of 5 Å to 100 Å and one of saidinsulating zones comprises an organic material, wherein said switchingdevice is switched from an off-state to an on-state under application ofa voltage exceeding a threshold voltage when said laminated structure isexposed to electromagnetic radiation.
 18. The switching device of claims16 or 17, wherein each of said insulating thin zones are formed byinsulating thin films of 10 Å to 500 Å thickness.
 19. The switchingdevice of claims 16 or 17, wherein said conductive or semiconductivezone is formed by conductive or semiconductive thin films of 5 Å to 50 Åthickness.
 20. The switching device of claims 16 or 17, wherein saidinsulating zones comprise monomolecular films or monomolecular built-upfilms consisting of an organic compound.
 21. The switching device ofclaim 20, wherein said insulating thin films are Langmuir-Blodgettfilms.
 22. The switching device of claim 21, wherein said insulatingthin films comprise Langmuir-Blodgett films comprising a compound havinga π electron level, a polymeric compound or a fatty acid.
 23. Theswitching device of claim 18, wherein said insulating thin filmscomprise thin films selected from the group consisting of oxide, nitrideand Langmuir-Blodgett insulating thin films and combinations thereof.24. The switching device of claim 19, wherein said conductive orsemiconductive thin films comprise a film made of a metal selected fromthe group consisting of Al, Ag, Zn, Sn and Pb or an alloy thereof, As₂Se₃, CdS, ZnO, GaAs or Si including single crystal silicon, polysiliconor amorphous silicon.
 25. The switching device of dlaims 16 or 17,wherein one electrode is light-transmissive.
 26. The switching device ofclaims 16 or 17, wherein said electrodes have a thickness of 2000 Å orless.
 27. The switching device of claim 16, wherein said conductive orsemiconductive zone has a thickness of 5 Å to 50 Å.
 28. The switchingdevice according to claim 16, wherein one electrode is lighttransmissive.
 29. The switching device according to claim 16, whereinsaid electrodes have a thickness of 2000 Å or less.